When optical fibers are connected to each other, or when an optical fiber is connected to an optical component, first the coating in an end portion of each optical fiber is removed to expose the glass portion thereof. After that, the surface of the glass portion of the optical fiber exposed after the coating removal is cleaned by wiping off residual parts of the coating or the like with apiece of gauze or the like impregnated with a solvent. After that, a part of this glass portion is cut off with a fiber cutter (creeper) so that the glass portion has a predetermined exposed length. Thus, a mirror-finished cut surface is obtained. Such a series of steps for terminal working in the end portion of the optical fiber are carried out individually with tools special to those steps respectively, or carried out with an automated apparatus.
Removal of coating from an optical fiber is carried out, for example, by nipping the coating of a single-core optical fiber with a pair of coating removing blades, making the blades eat into the coating, and pulling the coating from the optical fiber with the coating removing blades. FIG. 8 is a view showing examples of removal of coating from a conventional optical fiber. FIG. 8(A) shows an example of removal of coating with flat blades, and FIG. 8(D) shows an example of removal of coating with semicircular blades.
As shown in FIG. 8(A), when coating 1b of an optical fiber 1 is removed with a pair of flat blades 2, the upper and lower flat blades 2 and 2 are made to eat into the coating 1b shallowly enough not to come into direct contact with the surface of a glass portion 1a of the optical fiber 1. In this state, when the optical fiber 1 is pulled in the left direction shown by the arrow in the drawing, the coating 1b is ripped down at the place where the blades eat. Then, the coating 1b is removed while forming a swelling on the right of the blades.
When the outer diameter of the glass portion 1a is 0.125 mm and the outer diameter of the coating 1b is not larger than 0.3 mm, the distance between the pair of flat blades 2 will be about 0.2 mm, and the distance between the glass portion la and each flat blade 2 will be about 0.04 mm.
When the thickness of the coating 1b of the optical fiber 1 is small, pulling out the coating 1b may make the optical fiber 1 shake up and down. When the coating 1b is pulled out in the state where the optical fiber 1 shakes up and down, the pair of flat blades 2 and 2 further eat into the coating 1b so that the surface of the glass portion 1a of the optical fiber 1 is brought into contact with the blades. Thus, the surface of the glass portion 1a is apt to be damaged. When the surface of the glass portion 1a is damaged, the strength in connecting optical fibers to each other by fusion splicing is lowered so that the connection may be broken easily.
It is therefore known that a resin layer is added to a coating portion to be removed so that the thickness of the coating is increased, and the coating 1b is removed together with the added resin layer (see Japanese Patent Laid-Open No. 94925/1994). However, it requires extra labor to form the coating resin layer additionally for coating removal. In addition, when the upper and lower flat blades 2 and 2 are made to eat into the coating 1b, the sectional shape of the coating 1b becomes an elliptic shape as shown in FIG. 8(B). When the coating 1b is pulled out in this state, the end portion from which the coating 1b has been removed is expanded like an elliptic trumpet as shown in FIG. 8(C). Thus, there is also a problem that failure in shape is apt to occur in a molding step in which glass portions 1b are connected to each other by fusion splicing and the fusion splicing portion thereof is covered with resin or the like.
As shown in FIG. 8(D), when coating is removed with a pair of semicircular blades 3 and 3, first, the semicircular blade portions are made to eat into the coating 1b shallowly enough not to come into direct contact with the glass portion 1a. The semicircular blades 3 are steadier than the flat blades 2 when the optical fiber is pulled out. Thus, it is difficult for the optical fiber surface to abut against the blades.
However, when the optical fiber 1 is pulled out in the left direction shown by the arrow in the drawing, the coating 1b is ripped down at the place where the blades eat into the coating 1b, coating dust 1c is collectively concentrated on the right side of the blades. When the coating dust is concentrated, the pulling resistance increases so that it becomes difficult to pull out the optical fiber 1. When the optical fiber 1 is pulled forcedly, the optical fiber 1 will be broken. In addition, when the adhesive force between the coating 1b and the glass portion 1a is great, the coating dust is crushed to powder to increase the residual part of the coating 1b adhering to the glass portion 1b. Thus, the workability to remove the coating dust (residual part) deteriorates.
In order to facilitate the removal of coating from an optical fiber, there is also known a technique in which a heater is disposed in a coating removing apparatus and heating by the heater is used to weaken the adhesive force between the optical fiber and the coating. However, the aforementioned problem in coating removing blades themselves has not been solved.
It is an object of the present invention to provide an optical fiber coating removing apparatus which can carry out coating removal easily without damaging the surface of a glass portion of an optical fiber when the coating of the optical fiber is removed therefrom.
Further, it is another object of the present invention to provide an optical fiber coating removing apparatus which is excellent in workability because it can carry out positioning or the like for removing the coating of the optical fiber easily.